Functional Analysis of a Voltage‐Gated Sodium Channel and Its Splice Variant from Rat Dorsal Root Ganglia

• Published in: Journal of neurochemistry Vol. 70; no. 6; pp. 2262 - 2272
• Main Authors: Dietrich, Paul S., McGivern, Joseph G., Delgado, Stephen G., Koch, Bruce D., Eglen, Richard M., Hunter, John C., Sangameswaran, Lakshmi
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.06.1998; Blackwell
• Subjects: Alternative Splicing; Amino Acid Sequence; Animals; Biological and medical sciences; Cell membranes. Ionic channels. Membrane pores; Cell structures and functions; Dorsal root ganglia; Fundamental and applied biological sciences. Psychology; Ganglia, Spinal - metabolism; Ion Channel Gating; Male; Molecular and cellular biology; Molecular Sequence Data; Oocytes; Organ Specificity; Patch-Clamp Techniques; Polymerase Chain Reaction; Rats; Rats, Sprague-Dawley; Recombinant Proteins - biosynthesis; Recombinant Proteins - genetics; Recombinant Proteins - isolation & purification; Sodium Channels - biosynthesis; Sodium Channels - genetics; Sodium Channels - isolation & purification; Sodium Channels - physiology; Tetrodotoxin sensitivity; Voltage‐gated sodium channel; Xenopus laevis; Xenopus oocyte; Alternative splicing; Spinal cord; Rat; Nucleotide sequence; Xenopus laevis; Rodentia; Central nervous system; Amphibia; Salientia; Ionic channel; Gene expression; Vertebrata; Mammalia; Sodium; Spinal ganglion; Molecular cloning
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1046/j.1471-4159.1998.70062262.x

: Neurons of the dorsal root ganglia (DRG) express a diversity of voltage‐gated sodium channels. From rat DRG we have cloned and functionally expressed a tetrodotoxin‐sensitive sodium channel α subunit, NaCh6/Scn8a/rPN4, and a splice variant, rPN4a. Primary structure analysis shows NaCh6/Scn8a/rPN4 to be highly homologous (99%) to NaCh6 and most likely represents the same transcript. The splice variation in rPN4a is homologous in sequence and location to that of rat brain I. Tissue distribution analyzed by RT‐PCR showed NaCh6/Scn8a/rPN4 to be expressed at its highest levels in rat brain, at moderate levels in spinal cord, and at lower levels in DRG, nodose ganglia, and superior cervical ganglia and to be absent from sciatic nerve, heart, and skeletal muscle. In contrast, rPN4a shows no expression in brain and low‐level expression in spinal cord, whereas in DRG its expression is comparable to that of NaCh6/Scn8a/rPN4. Functional analysis of these channels expressed in Xenopus oocytes showed that NaCh6/Scn8a/rPN4 and rPN4a exhibited similar properties, with V1/2≅−100 mV for steady‐state inactivation and V1/2≅−40 mV for activation. rPN4a recovered from inactivation significantly faster than NaCh6/Scn8a/rPN4. NaCh6/Scn8a/rPN4 was inhibited by tetrodotoxin with an IC50≅ 1 nM. Coexpression of the β1 subunit accelerated inactivation kinetics, but the β2 subunit was without effect.